How do I keep from getting a shock while looking for an open ground?

I just installed 4 used fluorescent light fixtures in my garage. Two of them i tested independently and they worked fine. After installing all four i wired them up to two switches and put two fixtures on each switch. While strapping up the conduit as I had them all running I got a shock from the conduit. When I went to turn them off i also got a shock from the metal on the switches. Therefore obviously something is grounding out but I have no idea how to trace it without getting a shock each time i check one of the fixtures. Is there a way or tester that will tell me if the conduit or fixture is hot before i touch it to find out?